1893.] NEW YORK ACADEMY OF SCIENCES. 91 



I will leave the further consideration of the subject to some 

 future occasion. I will add, however, that Prof. Langley 

 (already quoted) has in the same publication tabulated the 

 speed at which planes of varing angles of inclination must be 

 driven against the air to rise and " soar," as he exj^resses it. 

 But in his experiments a rigid arm stretched out to keep his 

 Aeroplane constant in its field of action, and if we imagine that 

 this support is instantly severed, just as the proper speed to 

 cause the plane to " soar "is attained, the result is disastrous 

 to a continuous flight. Unless the plane is whirling, atmospheric 

 resistance immediately upsets it, and it falls in fantastic curves, 

 lifeless and inert, like a kite with a suddenly severed string. I 

 have stated that my boomerang is a whirling aerojilane, pure 

 and simple. And now that we have ascertained a definite 

 speed to cause it to soar, it is obvious that it cannot do other- 

 wise than return in a backward flight, after it progressive force 

 is spent. 



It happened that in explaining the principles involved to an 

 enquiring friend, I used the terra a " Gyrostatic domination." 

 He seemed to be quite satisfied for the time, but after a 

 moment's thoughtfulness he said : ' ' Doubtless you are right — 

 but I'll be hanged if I can see what makes it come back." 



I offered once a little prize for the best answer as to what 

 makes it come back, and I was favored with a large amount of 

 of correspondence from all sorts of people, but the most of 

 them rehearsed that abominable description in the cyclopedias, 

 about the oblique bars of the wind-mill, but the most remark- 

 able one of all, in fact the one which truly solved the problem 

 in the fewest words was from a mere child, and it was original. 

 It was a follows : 



* ' Dear Mr. Emerson : 



" I am a little boy nine years old. God makes the boomerang 

 come back." 



So to soar a little in amplification of this dear little fellow's 

 answer, it may be said that the same invisible arm which 

 stretches out with subtle power to hold the ponderous worlds 

 in their awful flight, gently upbears in open palm this simple 

 piece of whirling wood till its orbit is comjilete. 



But to descend to more definite and solid English, I prefer 

 the term " gyrostatic domination " to " parallelism of axis " in 

 exi^ressing tins sustaining force. " Fixity of the plane of rota- 

 tion " may be equally expressive. If, then, we give to our 

 whirling Aeroplane the definite speed required to cause it to 



